Carposina sasakii Matsumura is one of the most destructive fruit-boring pests of pome and stone fruit trees in eastern Asia. Because larvae complete their development inside a single fruit, larval density per fruit is a critical factor in their survival, development, and fecundity. The effect of larval density was examined to determine the ideal density for devising an economic and sustainable mass-rearing system for harvesting of C. sasakii. Mass production of insects of the same age of a specific stage is not only important in biological control, but also in pheromone extraction, culturing of entomopathogenic nematodes and fungi, etc. Life history data for six larval densities (1–5, 6–10, 11–15, 16–20, 21–30, and 31–40 larvae/apple) were collected at 25.5 ± 0.5°C, 75.0 ± 5.0% RH, and a photoperiod of 15:9 (L: D) h. Data were analyzed using the age-stage, two-sex life table. The results showed that the highest preadult survival rate (42.00%), fecundity (104.70 eggs), and population parameters (intrinsic rate of increase r = 0.0718 d^-1, net reproductive rate R₀ = 23.03 eggs, and finite rate of increase λ = 1.0744 d^-1) were observed at a density of 1–5 larvae/apple. However, when the rearing costs and production rate were considered, the density of 16–20 larvae/apple was the most economical for mass-rearing C. sasakii in order to achieve a daily harvest rate of 1,000 pupae (from 273 apples per day).To ensure the sustainability of the mass-rearing system, we included the life table variability in the harvesting strategy.